Cutting process for improving yield and cutting quality of large-diameter silicon carbide cutting blade

Abstract

The invention discloses a cutting process for improving the sheet yield and cutting quality of a large-diameter silicon carbide cutting sheet, and belongs to the technical field of silicon carbide cutting. The cutting process comprises the steps that (1) spiral steel wires are wound on a grooved wheel at equal intervals to form a plurality of parallel cutting wires, the center diameter of the spiral steel wires is 50-80 micrometers, and the tensile strength is larger than 4100 N / mm < 2 >; (2) the linear speed and the linear tension F of the cutting line are set, and cutting liquid is conveyed to the cutting line; and (3) the silicon carbide crystal to be cut is fixed through a workpiece mechanism, the workpiece mechanism drives the silicon carbide crystal to be cut to move towards the cutting line, the cutting line cuts the silicon carbide crystal to be cut till cutting is completed, and the silicon carbide cutting piece is obtained. According to the cutting process, the surface quality of the cutting blade can be remarkably improved while the cutting efficiency is improved, and the cutting blade with the total thickness deviation smaller than 4 micrometers is obtained.

Description

Technical Field

[0001] The present application relates to a cutting process for improving the output rate and cutting quality of large-diameter silicon carbide cutting blades, and belongs to the technical field of silicon carbide cutting. Background Art

[0002] As a typical hard and brittle material, silicon carbide single crystal has a Mohs hardness of 9.2 to 9.5, second only to diamond, which makes the processing of silicon carbide single crystal substrates very difficult. At present, the manufacturing process of silicon carbide single crystal substrates can be divided into several stages, including rough processing, cutting, grinding, mechanical polishing, chemical mechanical polishing, and cleaning. Among them, the cutting process is a key process in front-end crystal processing, and the surface quality of the cutting piece will directly affect the surface quality of the final wafer.

[0003] Multi-wire cutting has become the mainstream method in today's crystal processing, especially in the cutting of hard and brittle materials. It uses multiple metal cutting wires arranged at equal intervals to move back and forth at high speed, carrying a mixed cutting fluid to cut the crystal into multiple cutting discs at the same time. Today's commercial cutting machines can cut hundreds of cutting discs at a time. However, the current commercial cutting machines mainly use spiral steel wires above 100μm, which will result in low number of slices, poor cutting surface shape, and poor consistency of single-rod cutting discs.

[0004] Patent 202210479116.2 discloses the use of diamond wire with a wire diameter of 30-140μm to cut silicon carbide crystals, and believes that the smaller the wire diameter of the diamond wire, the smaller the tension of the cutting wire and the greater the maximum wire speed of the cutting wire. However, the cutting process is a complicated process, and this method of adjusting the tension and speed of the cutting wire has limited ability to improve the cutting efficiency and cutting surface quality, and it is difficult to obtain a cutting piece with a total thickness deviation of less than 5μm. Summary of the invention

[0005] In order to solve the above problems, a cutting process is provided to improve the yield and cutting quality of large-diameter silicon carbide cutting blades. The cutting process uses a large-diameter silicon carbide cutting blade with a diameter of 50-80μm and a tensile strength greater than 4100N / mm 2 The spiral steel wire is used as the cutting wire. The line tension and line speed of the cutting wire are calculated by the diameter and tensile strength of the spiral steel wire. This can significantly improve the surface quality of the cutting blade while improving the cutting efficiency, and obtain a cutting blade with a total thickness deviation of less than 5μm.

[0006] The present application provides a cutting process for improving the yield and cutting quality of a large-diameter silicon carbide cutting blade, comprising the following steps:

[0007] (1) Winding a spiral steel wire equidistantly on a groove wheel to form a plurality of parallel cutting lines, wherein the central diameter of the spiral steel wire is 50-80 μm and the tensile strength is greater than 4100 N / mm2 ;

[0008] (2) setting the line speed and line tension F of the cutting line and transmitting the cutting fluid to the cutting line;

[0009] (3) The silicon carbide crystal to be cut is fixed by a workpiece mechanism, and the workpiece mechanism drives the silicon carbide crystal to be cut to move toward the cutting line. The cutting line cuts the silicon carbide crystal to be cut until the cutting is completed, thereby obtaining a silicon carbide cutting blade.

[0010] The value of the line tension F in step (2) is between the following values ​​of F1 and F2:

[0011] F1=K'DS / 1000 Formula (1),

[0012] In formula (1):

[0013] D——nominal diameter of spiral steel wire, in mm;

[0014] S——nominal tensile strength of spiral steel wire, in MPa;

[0015] K'——minimum breaking tension coefficient of spiral steel wire;

[0016] F2=εS / L(V0-V1) Formula (2),

[0017] In formula (2):

[0018] ε—elastic modulus of spiral steel wire;

[0019] L—the maximum length of the cutting part, in mm;

[0020] S—Cross-sectional area of ​​spiral steel wire, in mm 2 ;

[0021] V0—Linear speed of the cutting line on the front traction roller, in m / s;

[0022] V1—Linear speed of the cutting line on the rear traction roller, in m / s.

[0023] Optionally, the value range of V0 is 10 to 30 m / s, and the value range of V1 is 15 to 35 m / s.

[0024] Since the fluctuation direction of tension is consistent with the speed difference, the adjustment of tension is also the adjustment of the synchronous error of line speed. The line tension and line speed of the cutting line are calculated and determined by the above formula, which can make the cutting parameters match the spiral steel wire, thereby greatly improving the cutting capacity while obtaining a cutting blade with good surface quality, which is convenient for industrial promotion and use.

[0025] The cutting steel wire plays the role of carrying mortar in the multi-wire cutting process. During high-speed operation, the cutting mortar is brought into the crystal by the wire mesh. Under the action of tension, the diamond powder squeezes the silicon carbide crystal to achieve crystal removal. The higher the cutting wire speed, the greater the amount of new mortar carried, and the cutting efficiency will be improved, thereby improving the BOW and WARP of the wafer. However, if the wire speed is too fast, it will be difficult for the diamond abrasive to enter the incision, resulting in increased friction between the steel wire and the ingot, causing the steel wire to vibrate left and right, resulting in serious wire mark defects.

[0026] At the entrance of the cutting blade area, the liquid is filled with liquid and there is a liquid overflow area, while a continuous film cannot be formed at the exit, and only local aggregation can be achieved. The steel wire is greatly worn here, which easily causes the overall total thickness deviation TTV of the chip to increase. Too low a line speed will result in low production efficiency. When the cutting line tension is increased, the bending BOW and warping WARP of the cutting blade will also be reduced, providing convenience for the next grinding process. However, excessive tension will cause the steel wire to break, and rewiring will introduce wire marks to the chip, affecting the increase of local thickness deviation (LTV). Too little tension will cause excessive stress and severe warping of the chip, affecting the removal rate of the next grinding, so a higher line speed is required to match the appropriate tension. The cutting line tension of the present application is calculated and determined by the two formulas (1) and (2), which can optimize the cutting process to the maximum extent to obtain a chip with low bending, low warping, and low thickness deviation.

[0027] Optionally, the main wave height of the spiral steel wire is 30-50 μm.

[0028] Optionally, the spacing between adjacent main waves of the spiral steel wire is 20-40 μm.

[0029] The height of the main wave and the spacing between adjacent main waves will affect the ability of the spiral steel wire to carry cutting fluid. Within the above range, firstly, it can greatly improve the effect of carrying cutting fluid, secondly, it can improve the cutting efficiency, thirdly, it can improve the surface quality of the cutting blade, and fourthly, it can reduce the loss of the spiral steel wire and the loss of silicon carbide material, thereby reducing production costs and improving the consistency of batch production of cutting blades.

[0030] Optionally, the cutting fluid includes cutting oil: diamond powder in a weight ratio of (10-12):1. The cutting oil as a solvent can play a lubricating role and take away heat during high-speed cutting. Similarly, the material can play a role of suspension, lubrication and cooling during the process of cutting into thin slices.

[0031] Preferably, the cutting fluid comprises cutting oil and diamond powder in a weight ratio of 10:1.

[0032] Optionally, the cutting oil includes 85-90 parts of mineral oil, 3-5 parts of rheological additive, 4-7 parts of surfactant and 1-2 parts of dispersant. The mineral oil, rheological additive, surfactant and dispersant mentioned above can be the materials commonly used in the grinding and polishing of semiconductors in the prior art, which will not be repeated here.

[0033] Optionally, the diamond powder has a particle size of 4-10 μm. The particle size of the diamond powder and the wave height of the spiral steel wire of 30-50 μm can improve the sand-carrying capacity of the cutting fluid and ensure rapid grinding and cutting of the crystal, and can also improve the surface quality of the cutting blade.

[0034] Cutting fluid has three functions: cutting, viscosity, and cooling. Suspensions with high suspension, high viscosity, and high lubrication can effectively reduce the surface damage stress of the wafer. During the cutting process, as the temperature accumulates over a long period of time, the molecular thermal motion accelerates, the intermolecular attraction decreases, and the viscosity decreases, resulting in a poorer adhesion of the particles on the steel wire, which in turn increases the TTV value of the cutting blade.

[0035] Optionally, the crystal to be cut swings relative to the cutting line during the cutting process, and the swing angle is 1 to 3 degrees. The swing angle is convenient for optimizing the cutting knife, and cooperates with the spiral steel wire to improve the force uniformity of the cutting part, avoiding the introduction of stress during the cutting process. At the same time, within the above swing angle range, as the swing angle increases, the sawing force can be increased and the surface roughness of the wafer can be reduced.

[0036] Optionally, the spacing between adjacent cutting lines is 20-40 μm.

[0037] Optionally, the diameter of the silicon carbide crystal to be cut is greater than 6 inches.

[0038] Optionally, the total thickness deviation of the cut piece obtained by the above-mentioned cutting process is less than 5 μm, the curvature is less than -22 μm, and the warpage is less than 50 μm.

[0039] Preferably, the total thickness deviation of the cutting piece obtained by the above-mentioned cutting process is less than 4 μm, the curvature is less than -20 μm, and the warpage is less than 40 μm.

[0040] The beneficial effects of this application include but are not limited to:

[0041] 1. The cutting process of the present application uses a spiral steel wire with a thinner diameter, which can reduce material loss during the crystal cutting process and increase the output rate, thereby reducing material costs and increasing the utilization rate of crystals.

[0042] 2. In the cutting process of the present application, spiral steel wire cutting has stronger cutting ability than straight steel wire cutting. Under the same crystal rod length, a faster cutting speed can be used for cutting, which is conducive to improving cutting efficiency. The coordination of spiral steel wire and cutting parameters can improve the surface quality of the cutting piece while improving the cutting efficiency. The total thickness deviation of the cutting piece is less than 5μm, the curvature is less than -22μm, and the warping is less than 50μm.

[0043] 3. The cutting process of the present application uses a spiral steel wire that presents different three-dimensional waveform effects at different angles, so that multiple recessed areas can be formed in the three-dimensional space. These recessed areas can store cutting fluid, thereby greatly improving the effect of carrying abrasives, and the cutting fluid attached to the steel wire is not easy to fall off with the movement of the steel wire, so that more abrasives can enter the cutting area to participate in grinding, thereby improving the removal efficiency and improving the surface accuracy of the cutting piece.

[0044] 4. The cutting process of the present application, the coordination of the spiral steel wire itself and the cutting parameters can increase the service life of the spiral steel wire and avoid the disconnection of the cutting wire, thereby ensuring the smooth progress of the cutting work. At the same time, it can also solve the problems of poor consistency of single-rod cutting blades and consistency of batch production cutting blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0046] Figure 1 This is a schematic diagram of a spiral steel wire with a central diameter of 80 μm involved in Example 1 of the present application.

[0047] Figure 2 This is a schematic diagram of the surface of the cutting blade involved in Example 3 of the present application. DETAILED DESCRIPTION

[0048] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0049] Unless otherwise specified, the raw materials in the examples and comparative examples of the present application were purchased through commercial channels, wherein the cutting oil was purchased from Remedy New Materials Technology (Suzhou) Co., Ltd.

[0050] Unless otherwise specified, the methods used in the examples and comparative examples of the present application are conventional methods in the prior art.

[0051] The present application relates to a cutting process for improving the yield and cutting quality of large-diameter silicon carbide cutting blades, comprising the following steps:

[0052] (1) Figure 1 The spiral steel wire is wound on the groove wheel at equal intervals to form a plurality of parallel cutting lines. The central diameter of the spiral steel wire is 50-80 μm and the tensile strength is greater than 4100 N / mm. 2 ;

[0053] (2) Setting the line speed and line tension of the cutting line, transmitting cutting fluid to the cutting line, and determining the line tension F of the cutting line;

[0054] (3) The silicon carbide crystal to be cut is fixed by a workpiece mechanism, and the workpiece mechanism drives the silicon carbide crystal to be cut to move toward the cutting line. The cutting line cuts the silicon carbide crystal to be cut until the cutting is completed, thereby obtaining a silicon carbide cutting blade.

[0055] Preferably, in step (2), the cutting fluid comprises cutting oil and diamond powder in a weight ratio of 10-12:1, wherein the cutting oil comprises 85-90 parts of mineral oil, 3-5 parts of rheological additive, 4-7 parts of surfactant and 1-2 parts of dispersant, and the value of the cutting line tension F is between the following values ​​of F1 and F2: F1=K'DS / 1000 formula (1), wherein: F1 is in N; D is the nominal diameter of the spiral steel wire, in mm; S is the nominal tensile strength of the spiral steel wire, in MPa; K' is the minimum breaking tension coefficient of the spiral steel wire;

[0056] F2 = εS / L(V0-V1) Formula (2), where: F2 is in N; ε is the elastic modulus of the spiral steel wire; L is the maximum length of the cutting part, in mm; S is the cross-sectional area of ​​the spiral steel wire, in mm 2 ; V0—the linear speed of the cutting line on the front traction roller, in m / s, and the value in the following Table 1 is 20m / s, V1—the linear speed of the cutting line on the rear traction roller, in m / s, and the value in the following Table 1 is 25m / s.

[0057] According to the above-mentioned cutting process, the following cutting operations of the embodiments and comparative examples were performed on a 6-inch silicon carbide crystal to obtain a silicon carbide cutting blade, and the curvature (BOW), warp (Warp) and total thickness deviation (TTV) of the cutting blades obtained in each embodiment and comparative example were tested. The specific parameters and test results are shown in Table 1. The cutting fluid used in Examples 1-14 and Comparative Examples 1-5 in Table 1 includes cutting oil and diamond powder in a weight ratio of 10:1, wherein the cutting oil includes 90 parts of mineral oil, 5 parts of rheological additives, 4 parts of surfactants and 1 part of dispersant. The cutting fluid used in Example 15 includes cutting oil and diamond powder in a weight ratio of 12:1, wherein the cutting oil includes 85 parts of mineral oil, 3 parts of rheological additives, 7 parts of surfactants and 2 parts of dispersant.

[0058] Table 1

[0059]

[0060] Figure 2 This is a test image of the surface shape of the cutting blade obtained by cutting in Example 3. It can be seen that the cutting surface shape of the cutting blade is of good quality and the cutting force in all aspects is more uniform. The total thickness deviation of the wafer after cutting is up to 5.0 μm, the curvature is up to -22 μm, and the warpage is up to 50 μm. The smaller warpage value facilitates the rapid thickness reduction in the downstream grinding process.

[0061] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. A cutting process for improving the yield and cutting quality of large-diameter silicon carbide cutting blades, characterized in that: The steps include: (1) Winding a spiral steel wire equidistantly on a groove wheel to form a plurality of parallel cutting lines, wherein the central diameter of the spiral steel wire is 50-80 μm and the tensile strength is greater than 4100 N / mm 2 ; (2) setting the linear speed and linear tension F of the cutting line and transmitting the cutting fluid to the cutting line; (3) The silicon carbide crystal to be cut is fixed by a workpiece mechanism, and the workpiece mechanism drives the silicon carbide crystal to be cut to move toward the cutting line. The cutting line cuts the silicon carbide crystal to be cut until the cutting is completed, thereby obtaining a silicon carbide cutting blade.

2. The cutting process according to claim 1, characterized in that: The value of the line tension F in step (2) is between the following values ​​of F1 and F2: F1=K'DS / 1000 Formula (1), In formula (1): F1 is in N; D——nominal diameter of spiral steel wire, in mm; S——nominal tensile strength of spiral steel wire, in MPa; K'——minimum breaking tension coefficient of spiral steel wire; F2=εS / L(V0-V1) Formula (2), In formula (2): F2 unit is N; ε—elastic modulus of spiral steel wire; L—the maximum length of the cutting part, in mm; S—Cross-sectional area of ​​spiral steel wire, in mm 2 ; V0—Linear speed of the cutting line on the front traction roller, in m / s; V1—Linear speed of the cutting line on the rear traction roller, in m / s.

3. The cutting process according to claim 1, characterized in that: The main wave height of the spiral steel wire is 30-50 μm.

4. The cutting process according to claim 1, characterized in that: The spacing between adjacent main waves of the spiral steel wire is 20-40 μm.

5. The cutting process according to claim 1, characterized in that: The cutting fluid comprises cutting oil and diamond powder in a weight ratio of (10-12):

1.

6. The cutting process according to claim 5, characterized in that: The cutting fluid comprises cutting oil and diamond powder in a weight ratio of 9:

1.

7. The cutting process according to claim 5, characterized in that: The particle size of the diamond powder is 4-10 μm.

8. The cutting process according to claim 1, characterized in that: The crystal to be cut swings relative to the cutting line during the cutting process, and the swing angle is 1 to 3 o .

9. The cutting process according to claim 1, characterized in that: The spacing between adjacent cutting lines is 0.5mm-1mm.

10. The cutting process according to claim 1, characterized in that: The diameter of the silicon carbide crystal to be cut is greater than 6 inches.

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